Bibliographic details of the publications referred to by author in this specification are collected alphabetically at the end of the description.
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.
Bermuda (or couch) grass (Cynodon dactylon) pollen is a clinically important seasonal aeroallergen in sub-tropical climates worldwide and in temperate climates where Bermuda grass is increasingly used in lawn mixes and to prevent soil erosion. In Australia, rye grass pollen is generally regarded as the most important seasonal allergen source, but of 736 patients in our allergy data base with seasonal asthma and/or rhinitis, 627 (85%) are sensitised to both BGP and rye grass pollen and only 100 (14%) are sensitised to rye grass pollen alone. Patients who have clinical seasonal allergy due to rye grass have symptoms in spring but with Bermuda grass pollen allergy peak symptoms extend into late summer in the southern hemisphere.
Pharmacotherapy is the mainstay of treatment for allergic diseases, but for appropriately chosen subjects, allergen specific immunotherapy (SIT) offers the opportunity to modify the natural course of the disease and has been shown to be highly efficacious and long-lasting in grass pollen allergy (Durham, S. R., Walker S. M., Varga, E. M., Jacobson, M. R., O'Brien, F., Novel, W., Till, S. J., Hamid, Q. A., N. Engl. J. Med., 341:468-475, 1999). Nevertheless, although SIT is accepted clinical practice for treatment of seasonal rhinitis, the treatment is seldom used in asthmatic patients for fear of inducing severe asthma or even anaphylaxis. In our allergy clinic, 50% of the patients with Bermuda grass allergy experience asthma and rhinitis. Therefore there is a demand for safer SIT regimens to permit wider application for treatment of Bermuda grass pollen sensitivity. With a growing appreciation of the critical role of T cells in the elicitation and regulation of the immune response to allergens, new T cell targeted strategies for SIT are being explored. Preparations which lack IgE binding reactivity but contain dominant T cell epitopes should be safe and effective.
Previous studies have identified multiple IgE-reactive proteins of Bermuda grass pollen using sera from Bermuda grass pollen-allergic patients, with predominant humoral recognition of one protein, Cyn d 1 (>76%), thus termed the major allergen of Bermuda grass pollen (Orren, A. & Dowdle, E. B., S. Afr. Med. J., 51:586-591, 1977; Ford, S. A. & Baldo, B. A., J. Allergy Clin. Immunol., 79:711-720, 1987; Shen, H. D., Wang, S. R., Atang, R. B., Chang, Z. N., Han, S. H., Clin. Allergy, 18:401-409, 1988; Matthiesen, F., Schumacher, M. H., Løwenstein, H., J. Allergy Clin. Immunol., 83:1124-1134, 1989). The cDNA encoding Cyn d 1 has been cloned and from the nucleotide sequence the primary amino acid sequence has been deduced (Smith, P. M., Suphiogl, C., Griffith, I. J., Theriault, K., Knox, R. B., Singh, M. B., J. Allergy Clin. Immunol., 98:331-343, 1996). There has previously been reported an analysis of human peripheral blood T cell recognition of Bermuda grass pollen in atopic Bermuda grass pollen-allergic and non-atopic subjects (Blaher, B., McCluskey, J., Puy, R., Czarny, D., Rolland J. M., Immunol. Cell Biol., 73:17-22, 1995). Both groups showed T cell proliferative responses to Bermuda grass pollen but the magnitude of response on average was greater in the atopics. Studies with other allergens indicate that a predominant Th2-type cytokine response to allergens further distinguishes those individuals with an allergic phenotype (Li, Y., Simons, E. R., Jay, F. T., HayGlass, K. T., Int. Immunol., 8:897-904, 1996). Clinical efficacy of SIT is reported to be associated with decreased production of IL-4 and IL-5 by allergen-stimulated T cells (Rolland, J. & O'Hehir, R., Curr Opin Immunol., 10:640-645, 1998). Therefore a thorough knowledge of allergen-specific T cell responses is required for improved SIT preparations.
T cell reactive determinants have not been reported for Bermuda grass pollen. Thus, detailed characterisation and elucidation of the immune response to Bermuda grass pollen or derivative thereof such as Cyn d 1, is critical in the development of specific diagnostic and immunotherapeutic methodology.
In work leading up to the present invention, the inventors have identified the human T cell epitopes of the Bermuda grass pollen, Cyn d 1. Further, in order to elucidate mechanisms of SIT, Bermuda grass pollen-sensitive patients were tested before and after standard immunotherapy using a tailored depot preparation containing 50% Bermuda grass pollen and 50% 7-grass mix. This preparation was used since there are minimal cross-reactive homologues between the Pooideae subfamily and Bermuda grass pollen (Marsh, D. G., Haddad, Z. H., Campbell, D. M., J. Allergy, 46:107-121, 1970; Martin, B. G., Mansfield, L. E., Nelson, H. S., Ann. Allergy, 54:99-104, 1985 and Suphioglu, C., Singh, M. B., Knox, R. B., Int. Arch. Allergy Immunol., 102:144-151, 1993). Therefore the standard 7-grass mix extract (Rye, Cockfoot, Bent, Kentucky Blue, Sweet Vernal, Timothy and Meadow Fescue) frequently used for immunotherapy of grass pollen allergy is unlikely to relieve symptoms due to Bermuda grass pollen sensitisation. Using oligoclonal T cell blasts, Cyn d 1 was shown to be a major T cell allergen of Bermuda grass pollen and three highly immunogenic regions of Cyn d 1 were identified. Following successful SIT there was a marked decrease in the allergen specific T cell proliferative response accompanied by a decrease in the IL-5:IFN-γ ratio. The identification of Bermuda grass pollen T cell epitopes now facilitates the development of molecules and methodology for the diagnosis and treatment of conditions characterised by the aberrant, inappropriate or otherwise unwanted immune response to Bermuda grass pollen or derivative or homologue thereof.